THE SNAPPING TURTLE. 227 
To settle the question more completely I cut the trachea of a Snapper across, and still 
found that the breathing went on at the ordinary rate. Next, a bent glass tube, two 
millimetres in width, was adapted to the upper end of the divided trachea and allowed to 
dip into water. ‘The water rose and fell in the tube about one millimetre only at each 
respiratory motion, and even this was clearly due to the synchronous reflex movements in 
the laryngeal muscles, which open and shut the glottis during the act of breathing,—a 
circumstance which is also observed to take place in higher vertebrates, as Dr. Dalton has 
well shown. 
Lastly, the bent tube was adapted to the lower end of the divided trachea and again 
dipped in water. At each inspiration the fluid was largely drawn up into the lung and 
rejected again during the subsequent expiration. It is, therefore, impossible to concede 
that this type of respiration is any other than that which is seen in mammals, and we 
must admit at once that the whole respiratory movement is effected in the Snapper as in _ 
them by the agency of thoracic and abdominal groups of muscles. 
I have, elsewhere, shown more fully the mode in which they effect this end and the 
part played by the various muscles thus employed. 
Respiration occurs in the Snapper about once in a minute in some cases, and often less, 
as once in two or two and a half minutes in others, while this animal undoubtedly has 
the power to exist a long time without breathing, when the process would invelve incon- 
venience. 
The respiratory process consists first of a full expiration, which is followed at once by 
a long and very large inspiration, and that again by a short and incomplete expiration, 
which still leaves the lungs more or less full until the time for the next respiratory move- 
ment arrives, when again a long expiratory act begins it. 
During the interval between two respiratory acts, a slight pulsatile motion is visible in 
the space between the two limbs and the carapax and plastron. ‘This movement appeared 
to be respiratory in its character, and to test the correctness of this view I resorted to the 
following plan. 
EXPERIMENT.—A large tube was placed in the lower end of the divided trachea, and a 
smaller glass tube* fitted to it and bent at an angle of 45 degrees. The open end was 
allowed to rest in water. In the intervals between the full respirations above described, 
the water rose and fell in the tube about 3 to 4 m.m., and this movement corresponded 
with the motion observed on the flanks of the animal. It was, however, so small in 
amount, the tube being only 2 m.m. in width, that it could scarcely be said to effect any 
change of moment in the mass of air in the lungs, and at the utmost could only be 
efficient in shifting slightly the air in contact with the various parts of the breathing 
* 2 millimetres wide. 
